1. Field of the Invention
The present invention relates to lithium secondary batteries.
2. Description of Related Art
Lithium secondary batteries have been adopted for various applications ranging from small-sized mobile devices, such as mobile telephones, notebook computers, gaming devices, and DSCs (Digital Still Cameras), to large-sized applications, such as power tools, power assisted bicycles, electric scooters, HEVs (Hybrid Electric Vehicles), and EVs (Electric Vehicles). Accordingly, much research and development efforts have been invested to obtain lithium secondary batteries with higher capacity and higher power.
Conventionally, alkaline aqueous electrolyte batteries, such as nickel-cadmium batteries and nickel-metal hydride batteries, which are relatively safe, have been used for high-power applications, so the lithium secondary batteries used for high-power applications need to have the same level of safety. It is therefore imperative to develop a high capacity and highly safe lithium secondary battery.
As a means for increasing the safety of a lithium secondary battery, Published PCT Application WO 2005/057691 A1 (Patent Document 1) describes that insulation performance between the positive and negative electrodes by providing a layer containing inorganic particles (hereinafter referred to as an “inorganic particle layer”) on the electrodes or the separator to prevent internal short circuits caused by foreign objects driving from the manufacturing process and the source materials